The ToBigInt conversion can have side effects, so the check for
neutered-ness must happen afterwards.

Bug: chromium:867776
Change-Id: I6e550c77a284da4cf132c21a6c3b1ed8f34eedc9
Reviewed-on: https://chromium-review.googlesource.com/1153553
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54761}